The present application discloses an application migration method in a mobile edge system, a related device, and a system. The method performed by a mobile edge orchestrator includes: obtaining a working index set of a to-be-migrated application on a first mobile edge server, where the working index set includes a migration index set including at least one migration index; determining a target migration solution of the to-be-migrated application based on the working index set and a preset correspondence, which is a correspondence between a migration index set and a migration solution; and sending a migration instruction to a mobile edge platform manager, where the migration instruction carries the target migration solution, and the migration instruction is used to instruct the mobile edge platform manager to migrate, based on the target migration solution, the to-be-migrated application from the first mobile edge server to a second mobile edge server.